Electrochromic devices

ABSTRACT

The invention includes many applications for electrochromic devices that require neutral colors and patterned electrodes. It uses novel materials, ways of making the materials, device configurations and applications. In one aspect, the device also includes electrical leads ( 115,116 ), transparent conductor layers ( 135,136 ), patterned EC layers ( 143,144 ), an etch line ( 99 ) and a substrate ( 125 ).

FIELD OF THE INVENTION

[0001] This invention relates to chromogenic technology and, moreparticularly, to the fabrication of chromogenic devices for applicationsrequiring variable electromagnetic radiation (UV, visible, infra-red,microwave, radiowaves etc.) transmission or reflection at the discretionof the user.

BACKGROUND OF THE INVENTION

[0002] Optical wavelengths are typically referred to as radiationencompassing UV, visible and infra-red wavelengths of about 200 nm to25,000 nm. Solar radiation on earth's surface is generally between 290nm and 2500 nm. Chromogenic devices for optical attenuation are ofseveral kinds, such as liquid crystal devices, suspended particledevices, user controllable photochromic devices and electrochromic (EC)devices (e.g., see WO 98/08137 for a description of such devices and thevarious kinds of electrochromic devices the complete disclosure of whichis incorporated by reference herein). All further discussions will belimited to the EC devices, although anyone familiar with art can extendthe principles of the disclosure here to the other chromogenic devicesas well. EC devices have several advantages, wide spectral response,wider temperature capability, generally non-polarizing attenuation,angle independent contrast, possibility of larger size scale-up, etc.The applications described below are discrete, however, many of theelements and concepts described here for one application may apply tothe others as well. In addition, many EC materials may change electricaland magnetic properties, and this change can be used to changetransmission of non-optical radiation such as radio and microwaves.

[0003]FIGS. 1a and 1 b show examples of typical electrochromic devicefabricated using two substrates, however many other EC devices can befabricated, some of them may only use one substrate.

[0004]FIG. 1a shows two substrates 120 and 121. These have conductivecoatings 130 and 131, respectively. An EC layer 140 is deposited on 131.The two substrates are connected using an electrolyte 150. The edges ofthe device are sealed using a sealant 170 to protect the inside of thedevice, and also to contain the electrolytic components. Power isapplied through the connectors 110 and 111 to change the opticaldensity. A DC voltage, typically less than 5 volts is applied across theconnectors to color the device. The ions are either inserted or expelledfrom the EC layer that causes a change in color. A correspondingreaction takes place at the interface of the electrolyte and the otherelectrode involving the redox species which is incorporated in theelectrolyte.

[0005] When the voltage is removed or reversed, the reactions alsoreverse.

[0006]FIG. 1b shows another type of EC device which has acounterelectrode (ion storage layer) 160 deposited on a conductivecoating 132 which is pre-deposited on a substrate 123. The othersubstrate 122 is coated with a conductive coating 133 and then with anEC layer 141. They are connected together by an electrolyte 151 andsealed at the edges by a sealant 171. Power is applied via theconnectors 112 and 113. In the bleached state the ions such as protons,lithium and sodium reside in the counter-electrode. Under an appropriatevoltage, these ions are reversibly extracted from the counterelectrode,travel through the electrolyte and are then inserted in the EC layer.This causes a change in transmission, i.e., coloration in the EC layerassuming that the EC. layer is cathodically electrochrornic. There mayalso be a simultaneous change in the optical transmission of the counterelectrode by expulsion of ions if it is anodically electrochromic.

[0007] Transparent means substrates which transmit part of theelectromagnetic radiation which is being modulated by the device.Examples of transmissive substrates are glass, plastics, silicon, etc.Some examples of transparent electrical conductors are coatings based onthin metal layers such as gold, palladiun, rhodium, alloys and dopedoxides such as tin oxide, indium oxide, zinc oxide and antimony oxide,and some of the preferred dopants in each of these oxides are fluorine,tin oxide, aluminum oxide and tin oxide respectively. The dopants may bepresent up to 25% concentrations (measured as atomic ratio of dopant tohost cations). The thickness of the oxide coatings is typically between10 nm to 10,000 nm. For metallic coatings the upper limit is around30-50 nm before they become optically opaque. There may be other layersbelow the transparent conductors, such as anti-iridescent layers,dielectrics, other metals, etc. Examples of EC materials are tungstenoxide, molybdenum oxide, iridium oxide, nickel oxide, polythiophene andpolyaniline. Typical thickness of EC layer is in the range of 10 nm toabout a 1000 nm. The electrochromic cell is assembled with the coatingsfacing inwards. A predetermined distance separates the two substrates.This distance or the gap is filled with an electrolyte which could be aliquid or a solid. The edge of the device is sealed for example with anorganic sealant (e.g., curable epoxy resin) or an inorganic sealant(e.g., solder glass) so that the interior of the device is protectedfrom the environment and the electrolyte (if liquid) does not leak out.The electrolyte thickness or the gap between the two substrates can becontrolled by the thickness of the solid electrolyte, spacers in theelectrolyte and/or the seals. Typical gaps are in the range of 5 micronsto 5000 microns, where gaps between 10 and 1000 microns are preferred.

[0008] The electrolyte in an electrochromic device in FIG. 1a will haveat least one polar solvent, one dissociable salt and a redox promoter inthe electrolyte. Sometimes the salt and the redox promoter may becombined into one such material as lithium iodide, viologen salt, etc.Examples of salts are NaCF₃SO₃, NH₄BF₄, LiClO₄, LiASF₆, LiBF4, LICF₃SO₃,Li N (CF₃SO₃)₂. Examples of redox materials are LiI, Iodine, viologensalts, phenothiazine, metallocenes such as ferrocene and itsderivatives. Examples of solvents are tetraglyme, propylene carbonate,ethylene carbonate, gamma-butyrolactone, sulfolane and its derivatives,acetonitrile and other nitrile solvents. Other additives such as UVstabilizers, fillers, opacifiers and viscosity modifiers may be used.Examples of UV stabilizers are benzophenones, benzotriazoles, metalcomplexes and combinations.- Some commercial examples are Uvinul 3035,Uvinul 3000 from BASF (Mount Olive, N.J.), the same from Ciba SpecialtyChemicals (Brewster, N.Y.) are Tinuvin 234 and from Cytec, WestPaterson, N.J., Cyasorb UV1164. Some viscosity modifiers are polymersand copolymers of polypropylene oxide, polyethylene oxide, acrylics suchas polymethylmethacrylate, and polyurethanes, etc. One may even havemonomeric additives and catalysts that will polymerize in-situ to yielda solid polymer or a higher viscosity electrolyte. Some of thesepolymerize by addition polymerization such as acrylic or acrylateterminated groups with free radical or ionic initiators, orpolycondensation such as isocyanates and hydroxy terminated groups withappropriate catalysts such as tin octoate, etc. Examples of componentsin such devices can be found in, e.g., U.S. Pat. Nos. 5,910,854 and6,045,724.

[0009] In FIG. 1b the redox promoter in the electrolyte is not necessaryas one of the EC or the ion-storage layer is intercalated with ions(typically protons, lithium, sodium, potassium, etc.) which are shuttledreversibly between the EC layer and the ion-storage layer. For an EClayer that colors upon reduction, these ions are inserted in thiselectrode for coloration and extracted for bleach. For anodic coloringEC layer the coloration occurs by expulsion of the ions and bleach byion-intercalation. Also, in an EC device the EC layer could be acathodically coloring layer such as tungsten oxide and molybdenum oxideand the ion-storage layer could also be an EC layer that colorsanodically, such as polyaniline and nickel oxide. Also due to theinsertion of ions in an electrode, refractive index changes areintroduced, and these changes could also be used for changing the lightpropagation direction, hence switching.

[0010] In FIGS. 1a and 1 b the two substrates are offset to facilitatean electrical connection to the conductive layers. One may even extendedthe conductive strip from the transparent conductor to the edge or theback side of substrate and then attach the connecting electrical wires,e.g., by soldering. The extension of conductive path on to the edges,etc., may be done using conductive solders, silver frits and conductivetapes.

[0011] An electrochromic device may be colored by varying the electricpotential applied to one substrate relative to the second. Tungstenoxide exhibits broad absorption almost in the entire range of solarradiation. Electrochromic devices can also be formed on singlesubstrates by sequentially depositing- an electronic (or electrical)conductor coating (such as tin doped indium oxide (ITO), fluorine orantimony doped tin oxide, gold, rhodium), an ion-intercalative layer(such as tungsten oxide, molybdenum oxide, niobium oxide, titaniumoxide), ion transport layer (such as tantalum oxide (proton conductor),lithium titanate. (lithium conductor), another ion intercalative layer(such as those described above and iridium oxide, nickel oxide, vanadiumoxide, polyaniline) and finally another conductor coating (examplesdescribed above). At least one of these conductors is transparent and atleast one of the ion-intercalative layer is electrochromic, i.e.,changes its color reversibly upon ion insertion and ion extraction. Allthe materials described above may be alloyed or combined with othermaterials as described in the art. Further, for purposes of thisinvention where non optical electromagnetic spectrum has to be varied,the electrochromic property of a layer in any of the above devices willbe extended in definition to include where the electrical conductivityof the EC layer will change reversibly upon ion insertion and ionextraction. Another kind of EC device will be included in thisdiscussion where a metal (copper, bismuth, etc.) is reversibly depositeddue to the electrochemical action on one of the electrodes, an exampleof this is in U.S. Pat. No. 5,903,382, which is incorporated byreference herein. In this invention the term switches, modulator andattenuators be will be used interchangeably as in a broader sense all ofthese imply where the intensity of the signal which passes through theseis changed.

SUMMARY OF THE INVENTION

[0012] In accordance with the principles of the present invention, thevariable light transmissivity characteristics of electrochromic devicesare employed to provide special effects in two areas:

[0013] 1) Those applications where an EC device is required, and wouldhave a neutral color during the range of coloration. This invention willdisclose dopants which can be used in tungsten oxide to yield EC layerswhich color to a neutral color during ion insertion and extraction.Primarily the neutral color is required between 400 and 750 nm forvisible light applications. Some of these are viewing devices needvariable neutral density filters: including gun sights, viewfinders,microscopes photographic filters and laboratory optical equipment andprojection.

[0014] 2) Those applications where patterned EC layers can be used asthey will demonstrate one of optical and non-optical effects (such aschanges in its electrical properties). We will also disclose reversibleattenuators for microwaves and radio-waves which are based on electricalproperty changes in the device. These patterns can find use in severalapplications including optical and non-optical communications such as inwaveguides. Examples of other applications of patterns are optical orelectronic camouflage, where moiré patterns of any type ofelectromagnetic radiation could be created actively without mechanicalmovement of substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1a shows an EC device without ion-storage electrode.

[0016]FIG. 1b shows an EC device with an ion-storage electrode.

[0017]FIG. 2 shows a patterned electrode which can be incorporated inthe EC device.

[0018]FIG. 3 shows a patterned electrode with two sections that can beindependently controlled.

[0019]FIG. 4 shows transmissive spectrum of an EC device in bleach andat various coloring potentials.

[0020]FIG. 5 shows an EC device which is capable of generatingelectronic Moire pattern

[0021]FIG. 6 shows examples of design patterns which can be used forforming Moiré fringe patterns.

[0022]FIG. 7a shows a lens with integrated EC element

[0023]FIG. 7b shows a lens with integrated EC element

[0024]FIG. 7c shows a zone plate where the pattern is formed by ECaction.

[0025]FIG. 7d shows a prism splitter where each wavelength segment canbe independently modulated by an EC device.

[0026]FIG. 8 compares transmission spectrum in the colored state of a ECdevice with neutral and blue coloring EC layer.

[0027]FIG. 9 compares transmission spectrum in the colored and thebleached state of an EC window device with high conductivity transparentconductors.

[0028]FIG. 10 compares transmission spectrum in the colored and-thebleached state of an EC window device with low conductivity transparentconductors.

[0029]FIG. 11 shows a reflective EC attenuator with locally thinnedconductor.

[0030]FIG. 12 shows a multiple reflective EC attenuator with locallythinned conductor.

[0031]FIG. 13 shows a waveguide cross-section consisting of an ECmaterial core.

[0032]FIG. 14 shows a waveguide core consisting of a section of an ECmaterial in the core.

[0033]FIG. 15 shows a waveguide cross-section core consisting of ECmaterial which can be colored in sections.

[0034]FIG. 16 shows a thermochromic device to modulate microwaves.

[0035]FIG. 17 shows an electrochromic device to modulate microwaves.

[0036]FIG. 18a shows a side view of an EC device to modulate microwaves.

[0037]FIG. 18b shows front view section of an EC device to modulatemicrowaves.

[0038]FIG. 19a shows the top view of an EC device to attenuatemicrowaves.

[0039]FIG. 19b shows front view section of an EC device to modulatemicrowaves through section B-B in FIG. 19a.

[0040]FIG. 20 shows six CV traces of a vanadium oxide sample overlappedover each other.

[0041] A complete understanding of the different embodiments of theinvention will be understood from the following detailed descriptiontaken in conjunction with these drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0042] The present invention is capable of being embodied in manydifferent applications that take advantage of the properties ofchromogenic devices utilizing the invention's unique properties toprovide the desired special effects. Several such applications arediscussed below.

[0043] Application Area—Sights

[0044] Electrochromic devices may be included in such sight applicationsas reticules, graticules, filters, stops and lenses which are used inoptical devices such as microscopes, telescopes, binoculars, gun sights,periscopes,—camera viewfinders, endoscopic viewfinders, theodolites,etc. where either of the two characteristics are required:

[0045] 1. To control the light transmission or reflection through theinstrument

[0046] 2. To display reversible (or erasable) information such asmagnification, scales, focus, comparators, etc.

[0047] Electrochromic elements can be introduced in the above-describedoptical instruments as filters, reticules, gratings, lenses, buffers andstops, etc. Electrochromic elements are particularly well suited fordisplaying information with high contrast and no angle dependence.Further, one may combine several such elements in one instrument, e.g.,one element may provide contrast control, another may displayinformation, be an electronic aperture, lens, diffraction grating, etc.

[0048]FIG. 2 shows a patterned EC coated substrate to be incorporated inan EC device for a gun sight. The tungsten oxide coating has been etchedto form a crosshair pattern. The figure shows a substrate 124, with atransparent conductor layer 134. The EC layer 142 is deposited in apattern form on the conductive layer 134. The electrical lead 114 isconnected to the layer 134 to apply power. The device can be madefollowing the scheme described in FIG. 1a or FIG. 1b. The patternedsubstrate is used as the EC layer. The pattern appears in the sight whenthe device is colored. Whenever the pattern is not needed, thecoloration is removed by applying bleach potential (which may be byshorting of the circuit, removing power, reversing the polarity,changing the voltage, etc).

[0049]FIG. 3 shows an alternative embodiment in which the transparentconductor has been etched to create two segments which are on the samesubstrate but are not electrically connected. This shows a substrate125, with a transparent conductor layer 135 and 136. These sections arenot electrically commuting, as the layer is separated in two parts bythe etch line 99. The patterned EC layer 143 and 144 are depositedrespectively on the two sections of the conductive layers. Also, wires116 and 115 are connected respectively to the conductive sections sothat power can be independently applied to these. In section 135 of thetransparent conductor the tungsten oxide has been etched to form acrosshair pattern while in the other section 136 it has been etched toform a calibration pattern. The counterelectrode (or the transparentconductor on the second substrate of the device (not shown)) may not beetched. For non-etched counterelectrode only one electrical connectionwill be required for this substrate. The purpose of this device is to beable to color each pattern independently. Segmenting of substrateswithin the same device is also discussed in PCT/US01/14360 filed May 4,2001. One could also etch both the transparent conductor and theelectrochromic layer to yield patterns, as long as these areelectrically connected to the powering leads via conductive paths. Theopposite electrode, which may have an ion storage electrode coating, mayalso be etched in a mirror pattern corresponding to the design on the ECelectrode and assembled so that the mirror image in one corresponds tothe image in the other.

[0050] Any other method such as evaporation, sputtering, chemical vapordeposition, plasma assisted methods, etc., can be used for deposition ofthe electrochrornic coatings. A preferred precursor and a method todeposit tungsten oxide by wet chemical method is described in patentapplication Ser. No. 09/443,109 (filed Nov. 18, 1999), patentapplication PCT/US01/14360 filed May 4, 2001, and U.S. Pat. No.5,277,986.

[0051] Example: Patterning Process of an EC Layer

[0052] Shipley (Shipley Company, Inc. 2300 Washington Street, Newton,Mass. 02162) Microposit 1813 photo resists was cast on to a tungstenoxide (composition of this lithium oxide doped coating was (Li_(0.3)W)O)substrate between 1000 and 3000 rpm. The tungsten oxide coating itselfwas deposited on a 15ohms/square ITO coated glass (ITO coated glass wasobtained from Applied Films, Longniont, Colo.). The substrate was thenheated on a hot plate at 115C for 1-4 minutes. A contact photomask wasaligned over the resist and the entire assembly was exposed to broadbandUV light in an Atlas Electric Devices (4114 N. Ravenswood Ave, Chicago,Ill., 60613) Sun Chex for 15 to 30 seconds. Photo pattern was thendeveloped in NaOH solution (solution concentration was 0.05 to 0.2 M)for 10 to 30 seconds (depending on the solution concentration). All thephoto-resist from the exposed area washed off without harming theunderlying tungsten oxide. This was rinsed with distilled water blowndry with clean nitrogen, then the developed pattern was baked for 15minutes at 150C to harden the photo-resist so that it can withstand ahigher concentration of the NaOH etching solution in the next step. Theexposed WO₃ was then etched using 0.25 to 0.75 M NaOH for 10 to 30seconds. The substrate was then rinsed with D.I. water and blown dry.The cross-linked photo resists was removed with acetone and thesubstrate was again rinsed with D.I. water and blown dry. None of theseprocesses harmed the transparent conductor. The resulting WO₃ patternwas subsequently used to make a electrochromic device as described inFIG. 1a.

[0053] Etching of the transparent conductor and or the electrochromicfilm can be done by lasers, such as CO₂ lasers, YAG lasers and UVlasers. One may also etch patterns by photolithographic technology usedin standard semiconductor processing. Printing methods such as padprinting and ink-jet printing could also be used to deposit patters ofthe electrochromic materials so that no etching is required. Theelectrochromic material precursor used for wet-chemically processedcoatings is used as ink in the printing application. An example of suchprecursor for depositing the tungsten oxide and other ion storageelectrodes are described above. One may even deposit the patterns of theelectrochromic coating directly by using molded replicas, akin to rubberstamping and pad printing.

[0054] The line width of the pattern for these applications can varyfrom 1 to 1000 micro-meters, more preferably between 5 and 200micro-meters. The smaller dimensions are preferred for those patternswhich are magnified before viewing. It is preferred that the refractiveindex of the patterned EC material is matched with that of theelectrolyte, particularly in the bleached state. The refractive index ofthe electrolyte can be changed by changing the medium constituents,i.e., solvent, plasticizer, polymer, salt type, concentration of these,and other additives. The refractive index of the EC material can bechanged by changing its composition, porosity and microstructure (e.g.,amorphous vs. crystalline). It is preferred that the refractive index ofthe two be within 0.1 of each other or more preferably within 0.005 ofeach other. Another alternative is to match the index of the transparentconductor to the EC layer, especially when the transparent conductor ispatterned and the EC layer is deposited as a continuous layer on top ofthis pattern.

[0055] The device surface facing the outside may have anti-reflectivecoatings, permanently marked patterns, colored layers, etc. These mayeven be deposited on additional substrates which may be bonded orlaminated to the device surfaces.

[0056] Application Area—Military Windows and Camouflage

[0057] Windows in military transportation, such as for trucks, tanks,ships, planes and submarines may require that the people and equipmentinside may not be seen from the outside via these windows, particularlywhen it is dark outside. These windows may still have to provide visionto the people inside to be able to see the surroundings.

[0058]FIG. 4 shows the transmission spectra in the bleached state andthe colored state at various voltages for an EC device which hasamorphous tungsten oxide as the EC layer (the composition of the layeris (Li_(0.3)W)O). The device is based on a construction shown in FIG. 1ain which the redox material in the electrolyte is ferrocene. The deviceis quite transparent to all visible wavelengths in the bleached state.In the colored state, is most transparent in blue and very low intransmission in the longer visible wavelengths. Thus, if the lightinginside the vehicle is a complimentary color to the window color such asred (600 nm and above), the inside light transmission will be highlyreduced to an outside observer, while from the inside the view will beas if looking through a blue filter. During those times when such asafety is not needed the windows can be bleached for maximizing theview. FIG. 4 also shows that changing the color potential can controlthe tint of the windows. Windows may also be darkened to control glare,reduce IR transmission from inside which may be seen by the adversaries.The electrochromic materials and the interior lights are preferablychosen so that they are complimentary in coloration as described.However, even if white light is used inside the vehicle anelectrochromic window will reduce its transmission to the outsideenvironment.

[0059] Military camouflage can be also made using electrochromic devicesto reduce the thermal signature, emissivity or change the visualappearance of the military buildings or transportation vehicles listedabove. For example, electrochromic mirrors or windows can be tiled onthe outer skin of these objects. When these are colored or changed fromone color to the other color, their appearance would change. Further thetiled EC devices may be programmed so that they are always changingrandomly or in a fixed sequence so that their images if taken will bedifferent when compared by an offensive team. Similarly, if theemissivity of the skin is controlled by coloring or bleaching thesewindows so that it matches those of the surroundings, such vehicles orbuildings will be difficult to detect. This camouflage is thuselectronically deployable by changing the skin characteristics. The ECdevices employed for protecting one object need not be all identical.For example there may be difference in the electrolyte layer or theelectrochromic coatings so that patterns in color and emissivity canblend well with the surroundings. One may even use the concept of Moiréfringes in the camouflage. Typically, Moiré fringes are actively createdor changed when one of the patterned substrate is mechanically moved(translated or rotated) against another patterned substrate. Here weactivate this electronically (i.e., without any mechanical movement).However, mechanical movement may be added to the electronic effectdescribed above.

[0060] To generate Moiré fringes a pattern is printed at least on one ofthe substrates (e.g., lines which are straight or curved on the outerface of one of the substrates). Etching the tungsten oxide makes asimilar or. different pattern. Assuming that these are straight parallellines as on the outer substrate, the pattern in the tungsten oxide ispositioned so that it appears rotated by a few degrees (less than 20degrees, preferably less than 5 degrees) as compared to the lines on theouter surface. When the tungsten oxide colors the interference of lightpassing through the two fringe patterns results in Moiré fringes.

[0061] This is explained in more detailed by looking at FIG. 5. Thisshows an EC device made by a substrate 224 which has a permanentlyprinted line pattern 281 on its outer face. The lines are substantiallyopaque with clear portions between them. The other face is coated with atransparent conductor 232. As an alternate, the print 281 could havebeen deposited below or above the conductive layer 232 on the samesubstrate face.

[0062] It is preferred that this pattern be conductive if deposited ontop of 232 facing the electrolyte 251. An example of such a conductivematerial in contact with the electrolyte will be gold as it will notparticipate in reactions with the electrolyte. Another substrate 522 iscoated with the transparent conductor 233, which is further coated witha patterned EC layer 241. A device is assembled as shown in FIG. 1a byjoining the two substrates with an electrolyte 251. It is preferable butnot a necessity that the index between the pattern in the bleached stateand the electrolyte be matched as described above. The matching shouldoccur for the wavelength of radiation which is expected to create theMoiré pattern. The EC pattern 241 in this example is identical to thepattern 281, but tilted by a few degrees around the normal to thesubstrate plane as shown. When the EC pattern is bleached an observeronly sees the pattern 281 from the light passing through this window.When the EC pattern colors a Moiré pattern is created.

[0063]FIG. 6 shows non-exhaustive samples of various patterns which canbe used for creating Moiré fringes. The spacing and the width of thelines could be varied to suit the purpose; also in the same patternthese spacings need not be uniform. FIG. 6a shows a pattern made byconcentric circles. FIG. 6b shows a pattern made by wavy lines. Two ormore patterns may be placed (or displaced) or rotated against oneanother to generate the mismatch which will give rise to Moiré fringes.FIG. 6c shows a pattern made of circular dots of non-uniform size. FIG.6d shows a pattern created by spots. FIG. 6e shows a pattern created bystraight lines. FIG. 6f shows a pattern made by converging lines towardsthe center. The number of such lines and their width increases as onemoves from the center to the outside border of the pattern. The width ofthe lines and their spacing could be as shown in these figures or theycould be much wider (e.g., by a factor of 10 or more, and may depend onthe electromagnetic radiation wavelength) or they could be much slimmer(but preferably greater than 10 times the average wavelength ofelectromagnetic radiation for which the Moiré pattern is beinggenerated). As explained earlier the Moiré pattern may also be generatedby the interference of two or more different patterns, say FIG. 6b andFIG. 6e, and in our invention at least one of which is generatedelectronically by a reversible EC (or any other chromogenic device, suchas liquid crystal) device.

[0064] One may sandwich two EC devices to. make a composite, where eachEC device generates a pattern when colored. The interference betweenthese two gives rise to the Moiré effect. In the bleach state thecomposite device is clear, but generates a Moiré pattern when both ofthese are colored. Another way will be to fabricate a device as in FIG.1b without any external patterns, where the counter electrode is anodiccoloring and the EC layer is cathodic coloring, and both of these arepatterned. The patterns for both electrodes are so chosen that thedevice changes from a clear state to a colored state. Moiré fringes aregenerated as the colored patterns on the EC and counterelectrode createthis interference.

[0065] Further, one of the patterns (usually on the outside of thedevice) can be mechanically oscillated in real time then the fringepatterns will change as well. One way is to have this pattern on a thirdsubstrate in the vicinity of the device, or a flexible net may be placedin front of the device which is oscillated.

[0066] Yet another novel way is to use the Moiré pattern for enhancingthe conductivity of the conductive electrodes. In a window or a mirrorconstruction at least one of the substrate and the conductive coating onit are transparent. To form the Moiré fringes one of the fixed patterncould be lines of a conductive metal such as gold which will increasethe conductivity of the substrate. These could even be metal lines whichare passivated. These busbar concepts are described in a patentapplication Ser. No. 09/347,807 (filed Jul. 2, 1998) the disclosure ofwhich is incorporated by reference herein.

[0067] Application Area—Lab Optical

[0068] Optical instrumentation uses several types of optical elementsmany examples of these are, collimators, lenses, irises, wavelengthselectors, diffirion plates, prisms, buffers, stops, modulators,interferometers and comparators. Such instrumentation is used inlaboratories for scientific research (spectrometers, radiometers,materials analysis, image analysis), medical diagnostic labs (e.g.,ophthalmic apparatus to check for metal particles in the eye, surgicalequipment, pathological equipment), optical networking, opticalcommunication test equipment) optical recording and retrieval, etc. ECtechnology can be used to make several components described above,particularly which need to be changed to condition signals, or use themfor multiple purposes as demanded by the user and to eliminate movingmechanical components.

[0069] To make a lens with active EC components one may get the lensingaction from the inactive components of the assembly such as thesubstrates or from the EC layers. For example FIG. 7a shows a side viewof a lens where the substrate has been shaped to provide the lensingactivity. The plano-convex substrate 126 is coated with a transparentconductor 736. Another such substrate 127 is also coated with atransparent conductor 137 on the planer side followed by an EC layer744. The two are bonded using an electrolyte 152 and then edge sealed(not shown) making a device similar to FIG. 1a. The electricalconnections can be made by tabs or grinding the opposite edges slightlyto expose the transparent conductor (not shown). Here the EC layers areplaner, meaning they do not vary in thickness, and follow the substratecontour. In FIG. 7b (side view of a lens) the tensing action is mainlyprovided by the variable thickness of the electrolyte 153. Thesubstrates 128 and 129 have a spherical bend where the insides of theseare respectively coated with the transparent conductors 138 and 139.Free surface 139 is further coated with an EC layer 145. The electrolytepreferably has a refractive index greater than 1.4. This will also givea device similar to FIG. 1a, where the intensity of optical radiationpassing through these could be modulated. FIG. 7c shows a front view ofa zone plate where the EC layer 146 is patterned on a transparentconductor coated substrate 220. As described in above figures this isincorporated in a device using another substrate (not shown). In thebleached state this pattern is not visible but it is in the coloredstate and acts as a zone plate (lens).

[0070] To pattern electrodes several methods can be used as describedabove. Fine patterns (sub-micron) using silicone molds andphotolithography can be generated inexpensively as discussed in thefollowing publication, which is incorporated by reference herein, namelyJ. A. Rogers, K. E. Paul. R. J. Jackman and G. M. Whitesides, “Using anElastomeric Mask for Sub-100 nm Photolithography in the Optical NearField”, Appl. Phys. Lett. 70, 2658 (1997); G. M. Whitesides and Y. Xia,“Replica Molding: Complex Optics at Lower Costs”, Photonics Spectra,January 1997, p. 90

[0071] This technology typically consists of the following steps:

[0072] 1. Preparation of a master relief pattern by photolithography orother techniques.

[0073] 2. Transfer of the negative of the pattern to a mould made byin-situ polycondensation of an elastomer polymer (For example a siliconeelastomer from Dow Corning (Midland, Mich.) Sylgard 184) to form anelastomeric mask.

[0074] 3. Contact printing of the pattern on to a substrate usingwet-chemical solution of the electrochromic material precursor.

[0075] 4. Processing of the pattern (such as firing at elevatedtemperatures).

[0076] As described above a pattern can be etched by selectivelyremoving the tungsten oxide layer. This pattern can be a diffractiongrating. Thus, when this element is energized a diffraction grating isobtained, which would diffract the outgoing light beam, otherwise it issimply a passive element in the instrument. The voltage or the depth ofcoloration of the pattern can control the strength of diffraction. Forexample, if helium-neon laser is used as the light source (at 632 nm),these can be strongly diffracted by the blue gratings of the tungstenoxide. The diffracted light beam spots are spatially dispersed, whichcan be tapped for further processing. Once the grating is erased, thesespots disappear. Thus this can be used as an optical switch to turn thespatially distributed diffraction spots on and off. Index matchingbetween the electrolyte and the electrode is preferred as explainedearlier.

[0077] Configurable lenses can be prepared using patterning methods. Onecould etch the tungsten oxide in a zone pattern of concentric rings asdescribed in FIG. 7c. When colored, the diffraction results in a lens,which will focus a parallel beam at its focal point, or make a pointsource placed at its focus into a parallel beam. Individuallyaddressable concentric rings can be used instead of a mechanicalaperture. The aperture is then closed down by selectively coloring eachsuccessive ring.

[0078] EC elements can be integrated in other optical elements such asprisms and filters. Example 7d shows a prism 221 which has a transparentconductive coating 231. Another transparent plate 222 is coated withstripes of transparent conductor 230 separated by non-conductive areasof the substrate, but preferably where such separations 280 are notoptically transparent. This striped layer is further coated by an EClayer 240 and then assembled with an electrolyte 250 to form a devicewith the prism. The stripes 230 can be individually activated and willonly result in coloring that part of the EC layer which is in contactwith the stripe. One may even pattern the EC layer conforming to thestripe pattern. The prism acts as a wavelength splitter. The variouswavelength sections will pass through the different stripes and theirintensity could be modulated independently. This type of principle canbe used for other multiplexers or de-multiplexer filters used in theoptical industry. A feedback loop can be used to control the intensityof the transmitted beams. An EC device without individual controlledelements described above will attenuate all of the incoming or theoutgoing beam.

[0079] Using an EC filter can change the color of the light. Forophthalmic instruments which locate metal particles in the eye, the ECelement can be colored electronically rather then inserting a mechanicalelement in the instrument. Further if the color is changed it acts likea filter being inserted in the light path which has several functions,such as control of light intensity and color, reduce chromaticaberration to get sharper images, reduce light intensity withouteffecting the depth of focus.

[0080] Electrochromic devices may also use materials which change colorwith changing voltage, typically such EC devices utilize materials basedon Lutetium compounds. In this case colors or wavelengths can beselected. Regardless of which color EC devices change to, they can becombined with a narrow band-pass filter to yield a variable transmissivedevice. This is particularly an advantage with the tungsten oxide baseddevices, since they absorb in a wide wavelength region, they can becombined with almost any band-pass filter in the visible and the NIRregion to yield a monochromatic modulator. This procedure is describedin U.S. Pat. No. 5,724,187. Modulated beams can be further used ininterferometry and signal conditioning depending on the desiredfunction. Electrochromic elements which offer neutral density are alsouseful. A preferred ND filter should be capable of attenuating between400 and 700 nm of the spectral range. Also at any level of coloration,we can define the neutral density as following: the optical density atany wavelength between 400 and 700 nm should be within ±0.2 of theoptical density at 550 nm, or more preferably within ±0.1. The nextsection describes preferred composition of EC electrodes for neutralcoloring devices.

[0081] Application Area—Filters For Photography

[0082] Filters are used extensively in photography and video systems.Filters are used to change the ambience and the mood of the settings.Further, many filters are required not only for various colors but evento change the depth of colors. Filters are also required which may notcover the lens completely, e.g., the top half part may be colored andthe rest colorless. Thus it gets very cumbersome to carry these filtersand time consuming to determine proper settings. Thus EC technology canbe used to provide filters that could be colored to different depth orto different colors as described above. These filters may also besegmented so that the segments can be tinted as selected by the user.For example, filters based on tungsten oxide and the constructiondescribed above can be used for variable blue filters provided theelectrolyte colors only a little or in a blue hue. Devices withelectrolytes using ferrocene redox materials with tungsten oxideelectrode will color blue, and these electrolytes containingphenothiazene (e.g., see U.S. Pat. No. 5,724,187) redox materials willcolor more neutral. Redox materials could be combined and/or tungstenoxide can be doped to get the desired color.

[0083] One may also choose an electrochromic filter where it only colorsin the near infrared (NIR) region. For example crystalline tungstenoxide is know to block NIR more effectively as compared to the visibleradiation. Amorphous tungsten oxide blocks in both the visible and theNIR. Crystalline tungsten oxide mainly modulates by a change inreflection and amorphous tungsten oxide by a change in absorption. Thismay be useful for cameras or other equipment (such as night visionequipment) which needs to work both during the night (using infraredradiation) and day (using visible radiation) and employs a CCD (chargecoupled devices) or CMOS (complimentary metal oxide semiconductor)electronic imagers. Thus during the day when the light is bright, onemay block the NIR so that the image is sharp and is not distorted by thechromatic aberration due to the NIR During the evenings when the visiblelight is low, one may allow the NIR radiation to go through to increasethe image brightness. One may even switch from one image to the otherduring the day or night, store these and compare them and/or digitallyprocess them to see the differences and get information which was nototherwise available.

[0084] Doping of tungsten oxide with individual element oxidesmolybdenum oxide (Yamada S., Kitao, M., “Large Area Chromogenics:Materials and Devices for Transmittance Control”, Lampert C. M.,Granqvist, C. G., eds., p. 246, The International Society of OpticalEngineering (SPIE)), or zirconium oxide (Siddle, J. R., WO 99/08153) orvanadium oxide (Krings, L., et. al., WO 97/22906) makes it more neutralcoloring. We have discovered that those compositions which are neutraland have good reversibility have two transition metal oxides as dopantsin tungsten oxide. These two dopants are vanadium oxide and molybdenumoxide. There may be other added dopants such as alkali metal oxides(such as lithium oxide, sodium oxide and potassium oxide) for improvingthe kinetics and other transition metal oxides to improve the UVresistance. Examples of preferred oxides for improving the UV resistanceare cobalt oxide, chromium oxide and copper oxide. The addition ofalkali oxides and the UV stability imparting oxides listed above aredescribed in U.S. patent application Ser. No. 09/443,109. Since thepreferred compositions of tungsten oxide may consist of more than two ormore oxides, it is very difficult to control their compositionaluniformity both spatially and through the thickness repeatedly by thosemethods where these coatings are deposited by building thickness usingmolecular dimensions such as vapor processes. Vapor processes includesputtering, evaporation, chemical vapor deposition, etc. The preferredroute to do this is by wet chemical method where all of these areuniformly mixed in a precursor form and then deposited. An example to dothis is described below.

[0085] Example: Preparation of a Neutral Tungsten Oxide Coating.

[0086] A tungsten peroxy ester (PTE) precursor is made from tungstenmetal as described in U.S. Pat. Nos. 5,457,218 and 5,277,986. A solutionwas made using 0.45 g of PTE/ml of ethanol. Separately 1.0 g ofmolybdenum (II) acetate dimer was reacted by dispersing in 25 ml ofethanol and titrating into the mixture 30wt% hydrogen peroxide at 0° C.Once all the molybdenum dimer had reacted with the peroxide as indicatedby formation of a complete solution the peroxide addition was stoppedand the mixture allowed to stir a 0° C. for 30 minutes. The product wasthen isolated under reduced pressure at 35° C. in a rotary evaporator.This product was then added to the PTE solution (27g PTE in 60 ml ofethanol) resulting in a green-yellow clear solution. Vanadia was addedto the solution in the form of HVO₃ in ethanol. The vanadia was preparedby an ion exchange method by dissolving 29.93 g of lithium metavanadiatein de-ionized water (4.9 wt % solution).

[0087] This solution was then passed through an ion exchange columnfilled with cation- exchange resin Dowex Monosphere 650C in H⁺ form. Thefinal solution was orange in color and transparent. This solution wassonicated at approximately 25° C. for 2 hours until it turned into ahomogenous gel of dark red color. Triethylamine was then added to thegel in the weight ratio 6.3 g (CH₃)₃N: 120 g HVO₃. After stirring for 2hours this resulted in a clear solution. This solution was concentratedunder reduced pressure in a rotary evaporator at between 38 and 40° C.to 6.6% of its total volume. The final product was then dissolved inethanol in a ratio of 0.42 g HVO₃/ml of ethanol. Based on 1 ml of PTEsolution, 0.19 ml Molybdenum containing solution and 0.161 ml vanadiumcontaining solution were mixed. This was used to deposit a coating onthe conductive side of TEC 8 (Obtained from LOF Pilkington, Toledo,Ohio) glass substrate of an approximate size of 8 cm×8 cm. The coatingwas deposited on a spin coater with its chuck rotating at 900 rpm. Thecoating was air dried and heated in a two step process as by firstheating the coating under a controlled humid atmosphere to 135° C.followed by heating under ambient atmosphere to 250° C. at a heatingrate of 11° C./min and holding at 250° C. for one hour. The finalcomposition of the coating was (Mo_(0.05)V_(0.1)W_(0.85))O, and itsthickness was 385 nm.

[0088] Devices were made as described in U.S. Pat. No. 6,178,034 usingthis and (Li_(0.3)W)O as EC coating. The counter electrode was anotherTEC 8 substrate with its conductive side facing inward. The electrolytethickness was 210 microns and the composition was 0.05 molart-butylferrocene and 1.0 molar lithium trifluoromethane sulphonate in asolvent mixture of 60:40 volume % propylene carbonate and tetramethylenesulfone.

[0089]FIG. 8 shows the spectra of these devices in the colored state.Clearly, the doped coating with Mo and V ((Mo_(0.05)V_(0.1)W_(0.85))O)exhibited a more neutral color and the standard one was blue. Thepreferred combined atomic ratio of V and Mo to W (i.e., ((Mo+V)/W) is0.03 to 0.4, and the ratio of Mo to V is 0.2 to 2. The small depressionin the colored state spectrum of this device at about 640 nm is causedby t-butylferrocenium in the electrolyte. This peak can be reduced oreliminated by substituting the redox material in the electrolyte eitherin full or in part. U.S. Pat. No. 5,724,187 describes examples ofalternate redox materials and a preferred one is phenothiazine.

[0090] Example: Compositions for Neutral Counter-Electrodes

[0091] To make devices such as in FIG. 1b, neutral coloringcounterelectrodes must be employed, such as those containing iridiumoxide. Further the composition of the EC and the counterelectrode can betuned so that if one of the electrodes does impart color, the other onewill impart a complimentary color to give a neutral appearance. As anexample, the tungsten oxide composition in an EC layer may be combinedin a device with anodically coloring nickel oxide counter electrodecompositions which color brown. Nickel oxide itself may be doped toresult in more neutral color. Here we will describe a novel compositionbased on vanadium oxide which contributes very little to the devicecolor and results in a color which is primarily dependent on the EClayer. Thus an EC layer described in the above example and combined in adevice with this counter electrode will result in substantially neutraldevices.

[0092] V₂O₅ is a known ion-insertion electrode. This electrode isbrilliant yellow in its bleached state, which is difficult to neutralizein a device only by the EC layer based on tungsten oxide. For examplecolor of such an electrode (200 nm thick on TEC 8 (TEC 8 is availablefrom LOF Pilkington in Toledo, Ohio) in its bleach state can be given ona L*a*b* coordinates as 80, −9.6,67. The b* value of 67 shows theyellowness in color. This value and if possible b* must be reduced forthis to effectively combine with the tungsten oxides described above forneutral devices. The procedure to make V₂O₅ coatings is described below.We discovered that vanadium oxide when doped with at least one of tinoxide and antimony oxide results in such coatings. These coatings can bedoped with antimony oxide and tin oxide. Other transition metal andalkali oxides can also be added as dopants.

[0093] As an example a preferred composition of a coating(Sb_(0.03)Sn_(0.4)V)O resulted in L*a*b* coordinates of 86, −4, 24. Asthis coating is low in color as seen by smaller a* and b* values. To theeye this appears faint yellow and when reduced by inserting Li⁺ ions itgoes to a faint gray color. Also, for effective counterelectrode thesematerials should be able to reversibly incorporate charge. The chargecapacity of the vanadium oxide coating was 29mC/cm² (process for makingthis coating is described later) and for the doped 330 nm thick coatingthe charge capacity was 24mC/cm². Preferred compositions will have theatomic ratio of (Sn+Sb)/V in the range of 0.2 to 0.6 and Sb/Sn ratio of0 to 0.5 in those compositions where both antimony and tin oxide arepresent.

[0094] Example: Preparation of V₂O₅ Coatings

[0095] This is a novel method and a vast improvement over the currentart. The current wet-chemical method described in the art can bedemonstrated in the published PCT application WO99/45169 and in Nabavi,M., Materials Science and Engineering, Vol. B3 (1989), p. 203. Althoughthe former publication describes coatings doped with lithium, but stillseveral drawbacks are evident from this. First, the coatings could notbe treated to high temperatures (typically less than 200C) as theiroptical quality decreased due to increasing haze. This severely limitedits charge capacity due to its amorphous state. In this patentapplication the best coatings had a charge capacity of less than10mC/cm².

[0096] When these procedures were followed, the solutions had poorcoating characteristics, i.e., the coatings were substantiallynon-uniform and high in haze. Further the shelf life (meaning that itcould be used to make reproducible coatings under similar conditionsafter storing the solution for a while) was so poor that the solutionswhen formed had to be used immediately. The second references yielded0.5 micron thick coatings, but its charge capacity was only about 10mC/cm². It is important that the EC device have sufficient chargecapacity per unit area so that high contrast can be obtained. We havedetermined this number to be greater than 20mC/cm² of the coated areaThus our purpose was to remove all these problems utilizing awet-chemical method. This should be achieved in one coating step to keepthe costs of the devices attractive. Generally to obtain thick coatingsone would coat followed by a heat treatment which is at least above theboiling point of the major solvent used in the coating solution medium,and then repeating this several times, and then giving a final heattreatment.

[0097] Our objectives were:

[0098] 1. To produce high optical quality (less than 10% haze,preferably lower than 5% haze) V₂O₅ coatings on commercial transparentconductors. Haze is measured according to ASTM D 1003.

[0099] 2. The coatings had to be above 200 nm in thickness, preferablyup to 400 nm, all produced in one coating step. The important aspect isany thickness in one coating step which will give a charge capacity of20mC/cm² or more in one step for economical reasons.

[0100] 3. Fast kinetics, where the charge reported above is extractedwithin 120 seconds.

[0101] 4. The solution had to be inexpensive and have good coatingcharacteristics.

[0102] 5. Good shelf life is important, preferably greater than one weekat room temperature.

[0103] Solution Preparation:

[0104] The coating solution was prepared using lithium metavanadate(LiVO₃) as starting material and using an ion exchange technique toconvert it to the acid (HVO₃) and using a base to stabilize the solutionand also enhance its coating quality. For the coating solution thecarrier solvent was ethyl alcohol. The procedure is divided into foursteps as follows:

[0105] Step I. Ion Exchange formation of HVO₃

[0106] Two chromatography columns of dimensions 41×500 mm were packedwith 200 g of dry resin (Cation-exchange resin Dowex Monosphere 650C inH+-form with exchange capacity -2 meqv/ml.). The columns were filledwith DI water and allowed to stand for 24 hours. 29.93 g of LiVO3 wasdissolved by heating to approximately 60° C. and stirred for one hour in574.7 g of de-ionized water (4.9 wt % solution). The solution was thenvacuum filtered through GF/F glass fiber filter (0.7 μm particleretention). The columns were flushed with water and the LiVO₃ solutionwas then added (to the column) and discharged through the column dropwise. To completely remove all the HVO₃ from the columns they wereflushed with de-ionized water. A clear liquid exiting from the columnindicated the end point. The time to pass the LiVO₃ through the columnwas 0.5 hours. The collected solution was orange in color andtransparent. After approximately 30 minutes dark red fluffy solidsformed and continue forming while standing for about 24 hours at whichtime it ceased. The resulting product was sonicated for two hours at astarting temperature of 25C and rising to between 30 and 50C. Thisresulted in a homogenous gel of dark red color.

[0107] Step II. Addition of Triethylamine (CH₃)₃N

[0108] Triethylamine was added to the sonicated gel in the weight ratio:6.3 g (CH₃)₃N: 120.0 g HVO₃ gel. After a few minutes of vigorous shakingthe gel breaks up and turns into a brownish-greenish transparentsolution. The solution was then sonicated for one hour resulting in aclear liquid with grayish a tint. The addition of organic base which inthis case was triethylamine, was important to achieve good coatingcharacteristics, good solution forming characteristics and shelf life.

[0109] Step III. Concentrating of the Above Solution via VacuumEvaporation

[0110] 3789 g of the solution with triethylamine from step II above wasconcentrated under reduced pressure at between 38 and 40° C. in a rotaryevaporator to 249.3 g. The consistency of the concentrated product wassyrup-like with a purplish-brown color. This material was very stableand could be stored for several weeks and possibly several months underambient conditions.

[0111] Step IV. Preparation of Coating Solution

[0112] 249.3 g of the “syrup” solution from step III above was dissolvedin 600.0 g of ethyl alcohol and mixed by rotation under ambientatmosphere for 20-30 mins to form the coating solution. The solution wasstored in a refrigerator at 4° C. and had a shelf life (meaning that itcould be used to make reproducible coatings under similar conditions) ofseveral months. The solution had a shelf life at room temperature ofseveral weeks.

[0113] Sample 1: Coating Deposition and Processing

[0114] The solution from step IV above was deposited by dip coating ontotin doped conductive glass “”TEC Glass” under ambient conditions (TECglass is made by LOF Pilkington, Toledo, Ohio)). At a withdrawal rate of13.2 cm/min the final thickness (after firing as described below) of thecoating was 275 nm and at a withdrawal speed of 18.7 cm/min thethickness was 400 nm. The coatings were heated in a two-step process thefirst involved firing under a humid atmosphere to a maximum temperatureof 150° C. (“Humid firing” or “humid treatment”) as listed in Table 1.The second firing process involved firing to 400° C. under ambientatmosphere with a heating rate of 4° C./min and holding at 400° C. forone hour (“High Temperature Firing”). The sample was cooled to roomtemperature at approximately 5° C./min. The coatings were transparentand yellow in color. The % haze of the 275 nm coating was measured usingan Ultra Scan Colorimeter from Hunter Lab (Reston, Va.) and was found tobe 10.3%. As will become evident from the following examples, inclusionof “Humid Firing” was important to reduce the haze in coatings with highthickness. “Humid Firing” for this invention is generally characterizedas keeping the coatings at any temperature above 60C for more than 10minutes, when the humidity is equal to or exceeds 50%.

[0115] The charge capacity was measured in a three-electrodeconfiguration using platinum as the counter electrode and Ag/AgNO3 asthe reference electrode. The solvent was 1 molar lithium perchlorate inpropylene carbonate. The sample size was 7 cm². Prior to measuring thecharge capacity the sample is cycled 6 times using the three-electrodesystem to check reversibility. This is done from −0.7V to 0.7V againstthe reference by increasing the voltage from one limit to the other andthen decreasing back to the first limit at 10 mV/second. The current isrecorded. A trace is made of current vs. voltage. These traces (calledC-V traces) from the six cycles have to visually overlap each other foracceptable reversibility. FIG. 20 shows the six traces beginning fromthe first trace. Then the potential of the sample is equilibrated at−0.6V (completely oxidized). A step potential from −0.6 to 0.2 voltsversus the reference is applied. The current is recorded versus timeafter the application of the step potential. This current decreases froma high value to about zero. The measurement is stopped after 120seconds. The charge below this curve is integrated and is divided by theactive area of the coating on the sample to get the charge capacity. Theelectrode the charge capacity of the vanadia coating (230 nm) wascalculated to be 35.5 mC/cm² (or 0.1mC/cm²-nm). All these measurementsare done at room temperature (nominally 25° C.). TABLE 1 Humid ovenfiring profile Step # T ° C. RH, % Time, min 1 25 40 5 2 60 60 20 3 15010 80 4 80 8 40 5 60 8 20 6 25 30 20

[0116] Samples 2 and 3: Coatings Prepared With and Without “HumidFiring”

[0117] Vanadium pentoxide coatings were prepared and deposited asdescribed in example 1 except that the coatings were given “HighTemperature Firing” without the “Humid Firing”. The final thickness ofthe coating deposited at a withdrawal rate of 13.2 cm/min was 275 nm.The haze value of the coating measured as described in example 2 was20.1%. Another sample was made by single dipping a TEC 8 substrate whichwas given a humid and a high temperature treatment. The sample thicknessafter firing was 325 nm. Haze value was 6.5% and the charge capacity was42.8 mC/cm².

[0118] Sample 4: Coating Prepared With a Different Precursor

[0119] Vanadium pentoxide coatings were prepared and deposited asdescribed in example 1 except that the starting material was sodiummetavanadate. At a withdrawal rate of 15.84 cm/min the final coatingthickness was 279 nm and the haze value was 8.8%.

[0120] Sample 5: Effect of Firing Treatment on Different StartingCoating Precursor

[0121] Vanadium pentoxide coatings were prepared as described in example3 above except that one set of the coatings was not given the “Humidfiring” step and another set was. A comparison of the haze and thicknessof the coatings is given in Table 2. TABLE 2 Firing conditionsThickness, nm Haze, % Standard (400° C., 1 hr) 169 4.59 Humid + standard170 1.98

[0122] The coatings of this invention are also usable for batteries,particularly thin film batteries due to their high charge capacity.

[0123] The EC devices should preferably conform to the specificationsfor neutral density described earlier. These filters can be used indigital photography, particularly where light has to be controlledwithout affecting the depth of focus (constant aperture opening). AlsoEC filters could be used to extend the dynamic range of the imagingsensors. Since the optical density of the EC filter is proportional tothe applied coloring voltage, the microprocessor in the camera can takethe applied voltage into account to calculate the real intensity beingimaged. Neutral coloring EC windows find applications beyond which arelisted here such as automotive windows and mirrors; and windows for avariety of transportation and architectural uses.

[0124] One may even use an EC window where the stops are a patterned ECdevice in the shape of frames, to select the area which needs to beimaged or recorded. For example one may choose from a 4:3 and 16:9format. As described in above in “Sights,” the filter can be segmentedin many areas, by etching fine lines in the transparent conductor andalso etching the EC layer and repeating the same on the counterelectrodeside if required. As long as each segment is individually addressableone could darken any number of segments coloring selected areas, e.g., aspot in the center of the lens. One may even use EC filters to color insuch a way so that near one edge a deeper coloration takes place whichfades gradually as one moves away from that edge (gradient filter). Oneconvenient way of doing this is using the device of FIG. 1a, or anydevice which has substantial back reaction, i.e., the device selfbleaches when the power is removed. The electrolyte gap could be sochosen that the back reaction is high. This current can be changed byelectrolyte composition and its thickness. Further, the magnitude ofthis current will depend on the device size, its geometry and the busbarpattern and on the device-area over which the coloration is needed. Onemay even taper the electrolyte gap so that the coloration is moresubstantial in wider gap and decreases in narrower gaps due toincreasing back reaction in the narrower areas. The camera filters maybe coated with antireflective coatings to increase the image sharpness.

[0125] The photographic filters or any of the other devices describedcan also combine EC feature (which is user tunable) with static filters.This means use of substrates or combination with elements which havespecific light transmission and reflection properties. Examples arecolored bulk substrates, substrates coated with colored coatings,antireflection, UV blocking and IR blocking coatings.

[0126] Other Surface Area Applications of EC Devices

[0127] Patterned chromogenic films incorporated in EC devices can beused to add utility and aesthetics in a variety of equipment. EC windowscan be used to provide various aesthetically unique surface treatmentsfor objects such as equipment cabinets for stereo and video systemcabinets, kitchen cabinets and appliance windows used in kitchen,entertainment, laundry, etc. When the equipment is not in use thewindows may be colored to hide the equipment by providing an overalldark surface appearance that obliterates the details of individualcomponents and controls or to protect the equipment from the naturalsunlight coming from building windows, halogen and mercury lamps, etc.Further, the button covers, and display windows on the equipment itselfcould have electrochromic covers to indicate which aspects of the systemare active or non-active by dimming certain windows. For those ECdevices where dimming takes place in the IR region (such as thosecontaining tungsten oxide), one could block the communication from an IRremote, thus providing a disabling feature. This feature can be used incontrolling the remote communication between objects such as inbuildings, automobiles, appliances and in defense (land, air and navy).An application area in defense is where the transmission windows inmissiles may be darkened (uniformly or in a pattern) and made toobstruct or distort (using a Moiré pattern described above) thewavefront of the impinging optical radiation, microwaves, etc., forprotection of the interiors, or prevent electronic or optical jamming ofthe systems.

[0128] EC windows can be coupled with transparent touch-sensitive panelsto form an interface or control panel. Such a window can be transformedfrom a transparent state to a control panel where the labels aredisplayed on demand. These panels could be integrated into applicationssuch as audio or video component cabinets, microwave ovens where thewindow also serves as the control panel, wine storage racks with frontwindows, projectors and the like. Additional functionality can be addedto these panels by segmenting the EC display such that a fully darkenedstate can also be achieved which could provide a concealingfunctionality. This would allow the panel to, hide and/or protectequipment or goods from undesirable radiation, e.g. protecting wine fromambient light. The panel could also be patterned such that informationcould be displayed allowing functional and aesthetic use of areas notpresently used for such purpose, e.g. display of wine cabinettemperature and humidity.

[0129] Application Area—Use of EC Devices in Projectors

[0130] EC devices can be used to modulate or cut (filter) light fromprojectors. It is well known that the life of high intensity lightsources is materially affected by turning them on/off. By inserting anEC device between the light source and the exit pupil the amount oflight can be throttled or patterned to cut the light in specific amountsor sections. Also since the coloration depth is continuously variable,such device can be used to cut off some intensity to highlight or toreduce the importance of that area during a presentation. One could makethe light tansmissive or reflective platform of the projector (e.g. anoverhead projector) from an EC device which is segmented, and segmentscan be controlled independently. Touching the specific area can darkeneach of the segments. The touch sensing can be provided on the outersurface of the EC device by adding another element. The addition can beby lamination. The touch sensor can work via a membrane switch orcapacitive means as known in the art. Alternatively it can be combinedwith an imaging feedback system (e.g., by using a camera) so that whenthe user points to information (physical touch or optically, e.g., bypointing a light beam) on the screen that area is selectively darkened.One may even be able to select areas which need to be projecteddepending on the presentation size and shape, e.g., electronic croppingof edges. The amount of cropping required could be automaticallyadjusted with an imaging control or done by a manual interface.

[0131] Application Area—Fiber Switching

[0132] Optical fibers and the related technology are rapidly beingadopted in communications and networking. All of these at present havebeen adopted to work in the NIR region. Typically the optical networking(or local area networking, LAN) takes place in the region of 800 to 900nm, and the telecommunications in the range of 1300 to 1700 nm. Manyprinciples described here are usable for all wavelength devices, such asfiber-optic lighting, but particular focus is placed in the abovewavelength regions due to high commercial interest. Many conceptsdescribed earlier, particularly for “lab optical” are applicable to thisarea as well.

[0133] Electrochromic technology, particularly based on inorganic oxidesand conductive polymers is suitable to modulate transmission in theseranges. Modulation of light for these applications is required for manyreasons, some of them are:

[0134] a. To control intensity and/or to block light. In one of theinstances where the intensity control is required if the light is beingsplit into a number of wavelengths (wavelength division multiplexing,WDM), but either the source or the amplifier (e.g., erbium doped fiberamplifiers in telecommunications) cause intensity variations amongstthese wavelengths due to non-equal emittance or gains, respectively.

[0135] b. To switch light from one path to the other.

[0136] c. To split the light beam in more than one path.

[0137] Some of the patents and applications which describe the use of ECelements for such applications are U.S. Pat. No. 4,245,883 and WO99/55023. Both of these references fail to describe EC devices which arereversible in a practical sense since the electrolytes discussed are ionconductors. There is no ion-insertion counterelectrode layer in thedevice or a redox additive in the electrolyte in the shownconfiguration, which will balance the reaction once the tungsten oxide,is colored. While such devices may color a few times, they fail to bereversible when subjected to thousands of cycles, particularly withincreasing temperatures. Thus, referring to WO 98/08137 cited earlier,one will either require an additional ion-storage layer as seen in FIG.1b or 1 f the same layer configuration is used as in U.S. Pat. No.4,245,883 or WO 99/55023 (also shown in FIG. 1a), then a redox additivemust be used in the electrolyte layer. Examples of redox additives canbe a metallocene such as ferrocene and its derivative, lithium iodide,etc. The above principles can be used to make reflective devices such asmirrors and half mirrors as well. The reflective coating can be on oneof the outer surfaces of the substrate or can be substituted for one ofthe transparent conductors.

[0138] Further, the EC devices use transparent conductors which reflectin the infrared (IR). FIG. 9 shows a spectrum of a device based onlithium oxide doped tungsten oxide and as constructed in FIG. 1a. Thehigh attenuation in the bleach state is caused by reflectance from thetransparent conductor which in this case was 15 ohms/square of fluorinedoped tin oxide. One has to use high transmission conductors so that theattenuation in the IR in the bleach state is low. One such method is touse Si for conductivity, which is described in “An ElectrochromicVariable Optical Attenuator (ECVOA)” by Nada O'Brien, et.al. inConference on Optical Fiber Communication, Technical Digest Series,1999. They use gold on the other side as this is a reflective device.The use of Si would be fine for telecom purposes, but not for the localnetworks (e.g., metro networks) where wavelengths of about 800 to 900are used. These wavelengths are absorbed or reflected by Si. In ourinvestigations we found that transparent conductor, such as ITO can beused for this purpose as long as its surface conductivity is greaterthan 25 ohms/square. Since the size of the devices is small (typicallysmaller than one square cm of the active area), this conductivity isadequate for EC devices in telecommunication applications. FIG. 10 showsthe characteristics of transmissive optical attenuator made using ITOwith a conductivity of 80 ohms/sq. This shows that the bleached statetransmittance can be increased in the infra-red region by changing thetransparent conductor. For networking applications conventionaltransparent conductors below or above 25 ohms/square may be acceptableas the attenuation at about 850 nm (FIG. 7) is not too low in thebleached state. For reflective devices the second conductive coatingneed not be transparent. A preferred material is gold, but others suchas rhodium and alloys of these materials will also be suitable.

[0139] We also found that one may be able to eliminate the conductor orreduce its thickness locally from one of the electrodes. This area isfrom where the light enters and exits the device. FIG. 11 shows areflective modulator based on these principles. Substrate 1124 is coatedwith a reflective conductor 1132 such as gold. This is further coatedwith an EC layer 1141, such as tungsten oxide. Another substrate 1123 iscoated with a conductor 1133 such as gold or ITO. A hole 1130 is etchedto remove the conductor. The device is assembled with the electrolyte1151 and sealed with a sealant 270. The sealant to contain the interioringredients and to protect from the environment is 270. The power isapplied via the connectors 211 and 212. As shown in this figure thelight beam 1180 enters the device through this hole 1130 and passesthrough the EC layer 1141 and is reflected from the conductor 1132 exitsthrough the same hole. This light suffers very little insertion loss(i.e., substantially all the light enters the device) as there is noconductor on the top substrate for reflecting this beam. The insertionloss can be decreased by further ensuring that there are antireflectivecoatings or GRIN lens on the outside surface of 1123, and that therefractive index of the electrolyte is as close as possible to thesubstrate and the EC layer and the substrate 1123, preferably within±0.4 or better. When the EC layer is colored the light beam isattenuated. The diameter of the hole 1130 (or its width if this is aslit) is dependent on the size of the beam and the average wavelength oflight, but it should be preferably less than the thickness of theelectrolyte 1151, more preferably less than one tenth of the thicknessof the electrolyte. If one does not want to completely remove theconductor, it can be thinned in this area to at least reduce the inputloss to less than half of the reflective loss caused by the conductor.The process of removal or thinning will be referred to collectively asthinning from a claims perspective.

[0140] Another device is shown in FIG. 12 where multiple reflections areused to attenuate the beam. This can result in higher beam attenuation.This can also be fast as the EC layer only has to be intercalated to asmall degree, but larger attenuation is achieved due to multiplestrikes. The device consists of similar components as described above,i.e., substrate 225 coated with conductor 234 and then EC layer 242,assembled with an electrolyte 252 to the other substrate 226 which has aconductive coating 235 and with two holes 2260 and 2261. This is sealedby a sealant 271. Power is applied via the terminals 213 and 212. Thelight beam 1281 enters the device through hole 2260 and passes throughthe EC layer several times due to multiple reflections and then exitsthrough the hole 2261. For example when crystalline WO3 is used for theEC layer, it changes from transmissive to reflective in the infra-redregion. Thus in FIG. 11 if the conductor below the tungsten oxide istransparent then the device will switch the beam from reflection totransmission, i.e., change the path of the light.

[0141] One could use the devices of this invention in the opticalattenuator systems described in WO 99/55023. Further, one can alsoincorporate GRIN (Graded Index Optics) lenses on one or both sides ofthe EC device, depending whether it is a reflective device or atransmissive one. For example, such lenses and lens arrays with gradientoptics are available from Nippon Sheet Glass (Osaka, Japan) under thename SELFOC. The high refractive index side of this lens could be usedas one of the substrates for the EC device.

[0142]FIG. 13 shows a buried waveguide (end view) in a silicon wafer228. The waveguide 243 is a long channel, and a cross-section of this isshown. Light enters the waveguide end surface which is shown (going intothe plane of the paper) and leaves at the other end (not shown). Theseends may have anti-reflecting layers, GRIN or other lenses for reducingreflection losses and focussing. These may also function as seals toprotect the waveguides from environmental ingress (typically oxygen andwater). For lenses to protect these ends they must be bonded on to thisarea. Typically for single mode at 1550 nm the waveguide channel widthand depth can be 1-10 microns. However these numbers can vary dependingif it is a single or multimode. The EC device shown is based on theexample of FIG. 1a. The silicon wafer could be “n” or “p” type so thatit has some electronic conductivity. The channel in the silicon wafer228 is filled by a higher refractive index EC material, such as amaterial consisting of tungsten oxide 243. This plate is separated by anelectrolyte 253 (which may be a thin film, polymer or a liquid) from theother conductor 236 which is deposited on another substrate 227. One maycover the waveguide with a thin film of electrolytic layer (not shown)such as tantalum pentoxide or a lithium niobate which is lower inrefractive index. The polymeric or liquid electrolyte 253 may still beused to complete the device as shown. Alternatively the device may becompleted only using thin films where a thin film electrolyte isdeposited (not shown) on 228 covering the waveguide 243, followed by acounterelectrode layer (not shown) and then followed by conductive layersuch as ITO (not shown). Further layers for sealing, etc may also bedeposited following the conductive layer. When a coloring voltage isapplied as shown in the figure through the terminals 214 and 215,tungsten oxide colors reversibly. This results in both absorption andchange in the refractive index. Both of these can cause a loss eitherdue to increasing absorption or loss in light as it is not guidedproperly through the waveguide. There may also be a change in the indexof the electrolyte along with the change in the EC material. This mayalso assist in signal control and attenuation.

[0143] As shown in FIG. 14 (top view of the waveguide) the EC material244 may only be in a part of the waveguide formed by 291, 244 and 290 ina substrate 229 such as silicon wafer. The path of the light through thewaveguide is shown by 282. The refractive index of 291, 292 and 244(particularly in the bleached state) is lower than the substrate 229.291 and 290 may be same or different materials which are not active froman electrochromic perspective. The refractive index of these shouldpreferably match that of the EC layer in the bleached state so that thelight losses at their interfaces can be minimized. These figures onlydemonstrate the principles, but one could embed an EC section in eacharm of an arrayed waveguide (AWG) to give a versatile and independentcontrol for each channel. The EC section may even be before splitting orafter coupling, so that all wavelengths can be attenuated at the sametime. One may use other substrate material other than silicon dependingon the features, e.g., it can be erbium and /or ytterbium doped glasseswhere such waveguides are used for amplification of light by couplingoptical pumps to these. Thus attenuation and amplification can happen inthe same waveguide as desired by the user. As an extension a EC sectioncan be put in the waveguide section attached to the pump but before itcouples with the signal to be amplified so that amplification can becontrolled.

[0144] For a waveguide shown in FIG. 15, the electrical connection isapplied via a transparent conductor 330 which is conformably depositedon the non-conductive substrate 320 (or the conductive silicon is firstpassivated with a transparent insulator (not shown) before the conductoris deposited). The channel is first coated with a lower refractive index(in relation to the EC material) but a conductive material, such as ITO.This is then filled with the EC material such as a material includingtungsten oxide. This is done by physical vapor deposition, chemicalvapor deposition or wet chemical methods. This is then planarized(polished) to remove the tungsten oxide from outside the channel. TheITO outside the channel is used as one electrode, and the rest of thedevice is made as in FIG. 13 discussed earlier.

[0145] Doping and changing its microporosity can tailor the refractiveindex of the EC layer. U.S. Pat. Nos. 5,457,218, 5,277,986 and 5,252,354describe the materials used to make EC coatings, whereas the publication(Cronin, J. P., et.al., Solar Energy Materials and Solar cells, vol. 29(1993), p. 271) describes some of the coatings formed by this processwhere their porosity was changed.

[0146] The complete EC device using the substrate in FIG. 15 is finishedby sequential deposition of electrolyte film, conductive film and then abarrier or encapsulation layer such as silica. Since in all of theconstructions in FIGS. 13 to 15 the electrolyte is in contact with theEC layer, this should also be lower in refractive index as compared tothe EC material. One may provide the transparent conductor not in acontinuous form but more as electrically non-commuting stripes which areparallel to one another and saddle the channel like a “U” shape and thenconforming to the flat surface as shown in FIG. 15 to make electricalconnections. If this is done it is preferable to coat the waveguidechannel with a material which has the same refractive index as thetransparent conductor (within ±0.05) so that when the transparentconductor and the EC material in the channel is deposited, the lightonly sees one refractive index in the cladding (i.e., the areasurrounding the EC material within the waveguide channel). As an exampleone can make a mixed titanium dioxide and silicon dioxide coating tomatch the refractive index by varying the concentration of theseconstituents. When the EC device is finished, the top conductor can becontinuous. All the stripes in the bottom conductor may be activatedsimultaneously or independently. When such stripes are all coloredtogether, it will result in the EC channel coloring in roughly the samepattern as the striped conductor. This means the light travellingthrough it will encounter a grating which is varying in refractive indexand absorption, or primarily in refractive index. This grating isreversible or user controllable. Thus, one can make at will gratings(e.g., Bragg gratings) which can be activated to impart specificfunctions known in the art, such as multiplexing, reflecting, etc. Thereare many variations to the theme, e.g., the device can be constructedusing the theme of FIG. 1b where a counterelectrode is deposited on thesecond transparent conductor. The waveguide may not be embedded, butsticks out of the surface like a ridge (called ridge waveguide).

[0147] For the wavelength multiplexed system shown in WO 99/55023, it ispreferred rather than individual elements, one physical element is usedfor all of the divided beams, but this physical unit is divided intoindividually addressable areas by etching lines on the conductive area.The EC elements can be located before multiplexers or afterdemultiplexers for tuning the intensity of individual beams, or betweenthese if a constant amount of reduction is required for all thewavelengths. Examples of EC device fabrication with segmented areas andother features are described in PCT/US01/14360 application, filed May 4,2001, which is incorporated in its entirety by reference herein.

[0148] As described in an earlier section one could use optical elementssuch as switchable gratings, lenses, or holographic patterns to providefunctions that were not possible before. These patterns can be changedfrom one state to the other, or made to appear and disappear by coloringthe patterned EC material. That is EC technology allows the fabricationof re-configurable optical elements.

[0149] For optical switches and waveguides where the beam path ischanged a better method is to use the property of the change in the realpart of the refractive index. Most electrochromic materials color byabsorption, i.e., due to a large change in the imaginary part of therefractive index. Popular materials such as those containing tungstenoxide and molybdenum oxide generally color by the injection of protonsand lithium ions. These ions are too small to cause large changes in theindex. For this it is preferred to employ larger ions such as sodium,potassium, rubidium, cesium and silver. The structure of theelectrochromic materials has to be more open to accept the larger ions,and some of the preferred for this are hexatungstates, Prussian blue,etc. Since the materials do not have to be electrochromic in the sensethat they change color, but they should be able to reversibly switchfrom high to low index, materials with tunnel structures and largeinterstitial gaps would be suitable for this use. These materials may bealso those containing vanadates and vanadium oxides. Also conductivepolymers may show large change in refractive index. For materials whichshow a large change in index, only a small amount of ionic insertionwill result in the desired change. This could lead to low switchingvoltages (lower than 1 volt) and fast kinetics.

[0150] Switches can be made where the cladding of fibers can be madeelectrochromic, so that a change in its refractive index will lead todissipation of light rather than transmission. Same can be used inwaveguides, where a change in index will lead to a change in thedirection of light transmission. These could be planar waveguides andchannel waveguides. Further, if the geometry and the properties areproperly tailored one could couple and uncouple (split) and causeinterference between adjacent channel guides (such as Mach Zehnder andMichaelson's interferometers). The EC material introduced in one of thearms of the interferometer can cause a phase change so that the lightwhen combined will interfere destructively or constructively dependingon the user requirements (user being referred to as also the controlsignal). As another example, waveguides may be combined with gratingswhich are electrochromic, however, the use of gratings is userselectable. Further, with EC since the properties can be changedcontinuously, one can select the extent or strength of these effects.All the elements described above made by EC materials which changesignificantly by absorption, can also be done by those materials whichchange significantly in their refractive index. This gives a designer anenormous freedom to make re-configurable optical components.

[0151] Application Area—Microwave Attenuation with EC and ThermochromicDevices

[0152] The electrochromic properties of several type of polymers can beused to make microwave shutter (windows) which can be controlledreversibly by a user or a controller (for example see “A microwaveshutter using Conductive Polymers”, T. L. Rose, et al, Synthetic Metals,Vol. 85 (1997), p 1439), the complete disclosure of which is includedhere by reference. The polymer changes reversibly from an insulating toa conductive state, which also changes its microwave attenuationproperties (which can happen by changes in absorption and/orreflection). This can also be accomplished by other materials whichchange from an insulating to a metal like conductive state. For example,tungsten oxide and Poly EDOT (From Bayer, Leverkusen, Germany) can bereduced (intercalated) by protons, Li and sodium ions. When thishappens, these materials go from an insulating to semi-conducting to ametal like state (e.g., see R. S. Crandall et. al. “Electronic Transportin Amorphous H_(x)WO₃,” Physical Review Letters, Vol. 39 (1977) p. 232,for tungsten oxide). In this publication H is a proton, but for generaldiscussion it can be replaced by lithium, sodium, etc. For example, inthe tungsten oxide when it is intercalated by protons, WO₃ matrixbecomes H_(x)WO₃ where “X” is the degree of intercalation. Thetransition from the semiconducting to conducting occurs when “X” isabout 0.3. Thus if the microwaves are most attenuated by the metallicstate, the device can be operated close to this limit i.e., x<0.3 tox>0.3, so that it only requires a small degree of intercalation so thatthe transition can be fast. Thus, for any matrix if the value of “X” isknown, the range where the device should be operated for a fast responsecan be optimized.

[0153] In the above referenced paper by Rose, et. al., the deviceresembled FIG. 1b where polyaniline was used as a anodic EC electrodeand manganese oxide was used as a passive ion-storage electrode. Use oftungsten oxide containing electrode (cathodic electrochromic) insteadmanganese oxide could have resulted in a better performing device asthis would have added to the modulation of the device. Further in thispaper, the speed of the 0.4 inch square device was low (about 10 minutesto switch from one state to the other) and cyclability was poor as themodulation of the device decreased very significantly after the firsttwo cycles. Further, use of PTFE substrate in the device is not tooappropriate as it limits materials which can be deposited at hightemperature, adhesion issues are severe (with coatings and adhesives forsealant) and does not have a high barrier to both oxygen and water whichlimits the longevity of the device. Thus, to make practical devicesthese problems have to be overcome, where on this size of the device thespeed should be less than 3 minutes, preferably less than 1 minute, mostpreferably less than one second; and cyclability should be high, atleast 1000 times, more preferably greater than 10,000 times. Thisinvention uses materials and devices as described in FIG. 1a and FIG.1b, which show the desired characteristics listed above. Preferredsubstrates are those with good barrier properties and hightransmissivity to the microwaves, some examples are glass, silicon,plastics coated with barrier layers such as silica, titania, etc.

[0154] These switches (attenuators or modulators or variabletransmission windows) can be used in many areas where antenna functionneeds to be disabled or an antenna selection has to be made and thussome windows need to be closed down. Another area discussed earlier isof camouflage and jamming (or distorting) the signals which passthrough. Thus the use of this can be in hand held devices such ascellular phones, mobile computers, microwave receiving antenna windowsfor buildings which may be communicating wirelessly with other buildingsand satellites. Use in wireless modules with local and/or metro or othernetworks, e.g., blue tooth modules. The use of these can be insatellites, missiles, defense systems (such as equipment, transportationvehicles).

[0155] Also, thermochromic materials may also be used for this purpose,such as vanadium (IV) oxide (VO₂) which in its pure form changes from aninsulator to metal at 68C. Composite materials which include the abovematerials at least as one of their components can also be used for thispurpose. All throughout the present text, when materials are mentioned,e.g., tungsten oxide, then this will include dopants with othermaterials as well, such as oxides of other materials. Similarly, VO₂ maybe doped with other oxides such as tungsten oxide to lower itstransition temperature.

[0156] Windows using conductive polymers and the materials describedabove can be made on rigid (e.g., glass, GaAs, silicon wafers orplastics) or flexible substrates (thin glass, Si and plastics (thicknessfor rigid substrates such as glass and Si should be less than 100microns)). Some of the preferred polymeric substrates are polyamide,polyimide, polyester and polycarbonate, however their barrier propertiesmust be improved by e.g., additional coatings or incorporating fillerswith barrier properties. Some example of the fillers are materials withflake like geometries such as mica, clay (Nanomer® from Nanocor,Arlington Heights, Ill.).

[0157] These devices may be discrete, inflexible or flexible. They mayeven have adhesive patches on one of their faces so that such devicescould be pasted on products like tapes. These could be produced on rollslike tapes where the back sides (release layer) is peeled and then it isbonded.

[0158] Application Area—Microwave Attenuator with Thermochromic Device

[0159] This is a thin film heater which is deposited by a conductivefilm on a substrate. The film is etched to give an element of a heateras shown in the FIG. 16. The top view of the device only shows substratealong with a thin coating of the conductor 331 which is etched (removed)as shown by the dark areas 321. This results in a long serpentine pathof the conductor from one end of the substrate to the other. Theelectric terminals 312 and 311 are attached to the conductive coating toapply the electric power to heat the device. The temperature of this maybe regulated by a controller, an inline PTC (positive temperaturecoefficient) element or any other known means. The heater materials maybe any conductive material such as chrome, copper, gold, stainlesssteel, etc. There may be other layers on top of this (not shown) toenhance the adhesion of the thermochromic material 341 which would bedeposited on top of this to complete the device. Other protective layersmay then be deposited. The side view shows the etched areas as channelsin the heater coating 331. The thermochromic coating 341 is also shown.The heater is activated to reversibly increase the temperature of thethermochromic coating through its transition temperature so that itsconductivity changes and it attenuates the microwaves above itstransition temperature.

[0160] The distance between the etched areas in the heater film shouldbe crafted to let the microwaves pass through when the vanadium oxide isbelow the transition temperature. When the heating is done than theseareas should be narrow enough so that the heating of the thermochromicfilm is uniform even in the etched areas. One may even use alumina orsapphire substrates or additional underlying coatings to ensure that thethermal conductivity is high. Other variations of the theme includedepositing a heater pattern on one side of a non-electrically conductivesubstrate (or bonding a heater element which has electricallynon-conductive spaces between the heater elements), and depositing athermochromic coating on the other side of the substrate, so thatheating is done through the substrate. Heating elements and patterns arefrequently used to heat up outside automotive mirrors and are availablefrom ITW Chrono Therm (Elmhurst, Ill.).

[0161] Application Area—Microwave Attenuators with Electrochromic Device

[0162]FIG. 17 shows an electrochromic device for microwave attenuation.It shows an electrochromic device 300 which can be made as shown belowin FIGS. 1a and 1 b. The electrolyte for a device as shown in FIG. 1aconsists of a salt, e.g., lithium triflate and a redox species such asferrocene which are dissolved in a polar material such as propylenecarbonate, sulfolane, etc. The electrolyte may have other ingredientssuch as PMMA for viscosity modification. With the above electrolyte apreferred EC layer is that containing tungsten oxide. If in the aboveelectrolyte the ferrocene is replaced by viologen then preferably apolyaniline or polypyrrole coating can be used to replace the tungstenoxide (e.g., see U.S. Pat. No. 5,729,379 for highly reversible devicesusing polymeric electrodes with redox materials). The thickness of theTC (typically indium tin oxide and fluorine doped tin oxide) can bebetween 100 nm to 1000 nm. For the EC layer it can be between 100 nm to5000 nm. The liquid or polymeric organic electrolyte the thickness canbe 10 to 10,000 micrometers. The outside metallic aperture 380 (a holein a conductive coating or a foil deposited or bonded to the EC device300 ensures that the microwaves do not leak from the sides of the device300. Alternatively, one may make EC window device with acounterelectrode can be made only on one substrate. by depositing thinfilms sequentially of transparent conductor, EC layer, ion conductor,counter-electrode followed by another transparent conductor coating andtypically followed by a sealing layer as well known in the art. In thiscase the major difference will be in the electrolyte layer (or ionconductor) which will by typically 100 to 1000 nm. Some examples ofinorganic ion conductors amenable to thin film deposition are tantalumoxide, lithium-titanate, lithium-niobate, etc. Details of layerdeposition and device assembly can be found in several of the earlierincluded references.

[0163] If the continuous transparent conductive coating (TC) is tooattenuating then strips of conducting material, such as the TC ormetals, e.g., gold can be used. In all the devices mentioned inconnection with the present disclosure, whenever, a metal layer is usedinside the device, it should be non-reactive to the components it comesin contact with, which are typically EC layer, electrolyte layer andcounterelectrode. Typically, gold is quite non-reactive under mostelectrochemical conditions which the devices operate on, otherwise themetals have to be passivated as described earlier via a reference.

[0164] An example of a device with stripes of conductors is shown inFIG. 18a. Side view shows a device similar to FIG. 1a, where substrate322 is coated with conductive stripes 332 (such as gold) and then an EClayer 342 (such as tungsten oxide) is deposited on this. Thiscommunicates via the electrolyte (or ion-conductor) 350 with the othersubstrate 323 which also has conductive metallic stripes 333. Power tothe device is applied via the electrical leads 313 and 314. The stripesin the conductor are more clearly seen in section A-A (FIG. 18b). Asshown, the stripes on both electrodes may be parallel or alternativelythey may be rotated with respective to each other, and may not even bestraight stripes. The spacing between the stripes may be closely relatedto the microwave being attenuated. For example, for a 30 GHz microwave,the wavelength is 0.01 cm. Thus the spacing may be smaller or largerthan this to tune in the effects of diffraction. The strip pattern andspacing on the two substrates may also be different. One may deposit ionintercalative counter electrodes on the transparent conductor which istouching the electrolyte. These can be conductive polymers, such aspolyaniline, vanadium oxide, etc which are well known in the literature.Typically when such counter-electrodes are used, then a redox materialis not used in the electrolyte and one of the electrodes. When thedevice is powered to color a continuous sheet of conductive material,i.e., either the conductive electrodes or the conductive EC material,which reflects the microwaves. In the bleached state they pass throughthe non-conductive spaces between the inter-digited electrodes. Thedevice discussed below also has similar operating principles.

[0165] Another way would be making this kind of structure as describedin FIG. 19a where both electrodes are on the same surface. Theelectrodes are inter-digited 334 and 335 as shown in the top view alongwith the terminal connections 315 and 316 for powering. The dark areasis where the electrodes are located on the substrate. The front view inFIG. 19b taken through the section BB shows the complete devicestructure. The layer 390 is an insulating or an ion-conducting materialsuch as silica, tantalum oxide, etc., this prevents a short between theelectrodes 334 and 335 when the tungsten oxide colors. The tungstenoxide or the conductive polymer EC layer is shown as 343. Theinter-digited electrodes are shown as 334 and 335. The electrolyte 351can be a liquid or a polymer. This is sealed by using a sealant 371 anda cover plate 325. The fundamental guts of the device structure aresimilar to the one in FIG. 18, where the two electrode sets are onseparate substrate and are connected by a liquid or polymericelectrolyte. The device can also be of the type shown in FIG. 1b, and inthis case a counterelectrode layer will be incorporated the electrode334, one may even eliminate the insulating layer 390 and substitute thiswith the counterelectrode.

[0166] These electrodes can be processed by standard semiconductorprocessing methods using photo-resists, masks, etching and deposition ofsequential layers. The layers can be deposited by physical vapordeposition, chemical vapor deposition or by liquid (e.g., sol-gel, orsolvent casting) techniques. An aperture can again be supplied on theoutside of the window as discussed earlier. If a counterelectrode isused it can be provided on the tip of that set of inter-digitedelectrode which is in contact with the electrolyte. The layerthicknesses are described above, but the insulating silica or thetantala layer can be 10 to 1000 nm thick. In this device when the EClayer is non-conductive, the microwaves can pass through theinter-digited electrodes, however, when the EC layer is colored, thereis no normal path for the microwaves to pass through as it sees acontinuous conductive layer. The overlap between the EC layer on theinsulating layer should be sufficient so that it covers theinter-digited electrode below (or leaves a small enough space which arenot penetrated by the microwaves).

[0167] Attenuation (including reflection) of the microwaves or RFradiation in 1 to 100 GHz, is also dependent on the type of substratewhich is chosen. A TC coating can be put on this substrate which hasjust enough sheet resistance so that the EC device can work, but it willhave only a small impact on the RF attenuation (as measured byshielding). Since the wavelength of RF radiation from 1 GHz to 100 GHzcan vary between 0.003 to 0.3 m, one could use the substrate thicknessas well to design the right RF response. One may make integrated deviceswhere different parts of the device attenuate (control) different typeof electromagnetic radiation, such as optical and microwaves, or thesame part may control both. As an example the devices in FIGS. 13 to 16can control both. For example in FIG. 13, thermochromic property of VO₂effects the transmission in the IR as well as its conductivity changes,In FIG. 16, use of material containing tungsten oxide will alsoattenuate visible, and IR radiation while changing its conductivitywhich is useful for modulating the microwaves.

[0168] The above discussion has generally described discrete EC orthermochromic elements. However, it will be apparent to those skilled inthe art that it is also possible to integrate these elements on the samesubstrates where the other components are located. This results in“integrated optical modules”. Such integrated modules may have solidstate laser emitters (vertical cavity lasers), wave guides,multiplexers, demultiplexers, amplifiers, switches and signalconditioners on a single substrate. EC materials may be used in severalof these such as in waveguides, signal conditioners, switches,multiplexers and demultiplexers. Further and other modifications will beapparent and may be implemented by those skilled in the art without,however, departing from the spirit and scope of our invention.

1. A counterelectrode for use in an electrochromic device comprisingvanadium oxide doped with at least one dopant selected from the groupconsisting of tin oxide and antimony oxide.
 2. An electrochromic devicehaving an electrochromic layer including an electrochromic coating and acounterelectrode according to claim
 1. 3. An electrochromic deviceaccording to claim 2 wherein the electrochromic coating comprisingtungsten oxide.
 4. An electrochromic device according to claim 3 whereinthe electrochromic coating additionally comprises at least one dopantselected from the group consisting of alkali metal oxides and transitionmetal oxides.
 5. An electrochromic device according to claim 4 whereinthe alkali metal oxide dopant is lithium oxide, sodium oxide orpotassium oxide.
 6. An electrochromic device according to claim 4wherein the transitional metal oxide dopant is vanadium oxide,molybdenum oxide, cobalt oxide, chromium oxide or copper oxide.
 7. Anelectrochromic device according to claim 3 wherein the electrochromiccoating has an atomic ratio of vanadium and molybdenum to tungsten is inthe range of 0.03 to 0.4 and the ratio of molybdenum to vanadium is inthe range of 0.2 to
 2. 8. A method of making an electrochromic coatingaccording to claim 3 comprising the steps of: (a) preparing a solutioncomprising soluble sources of tungsten, vanadium and molybdenum and anorganic solvent; (b) applying the solution to a substrate; and (c)heating the substrate to form the electrochromic coating thereon.
 9. Amethod according to claim 8 wherein the step of preparing the solutioncomprises combining (i) a solution of tungsten peroxy ester in ethanolwith (ii) the product of the reaction of molybdenum (II) acetate dimerand hydrogen peroxide and with (iii) a solution of vanadic acid inethanol.
 10. A method according to claim 8 wherein the heating step iscarried out at a temperature of about 250° C.
 11. In a method for makinga vanadium oxide-coated substrate comprising the steps of (a) combining(i) an organic solvent, and (ii) a soluble vanadium source to form asolution; (b) applying the solution to a substrate; and (c) heating thesubstrate to form a coating thereon, the improvement comprising addingan organic base to the solution prior to applying the solution to thesubstrate.
 12. A method according to claim 11 wherein the organic baseis triethylamine.
 13. A method according to claim 11 or 12 wherein theheating step includes a humid firing step.
 14. A vanadium oxide coatingmade by the method of claim 13 and having a charge capacity of at least20 mC/cm² and a haze less than 10%.
 15. A method according to claim 11,12, 13 or 14 wherein step (a) comprises, in addition, combining asoluble lithium source.
 16. An electrochromic device having anelectrochromic layer comprising a patterned tungsten oxide coating andhaving a patterned, planar substrate.
 17. A device according to claim 16wherein at least in one state of coloration the pattern on the coatingand the pattern on the substrate interfere to provide Moiré fringes. 18.A device according to claim 16 or 17 wherein the pattern on the coatingis selected from the group of patterns consisting of concentric circles,wavy lines, circular dots of non-uniform size, spots, straight lines andstraight lines converging toward center.
 19. A device according to claim16 or 17 wherein the pattern on the coating and the pattern on thesubstrate are selected from the group of patterns consisting ofconcentric circles, wavy lines, circular dots of non-uniform size,spots, straight lines and straight lines converging toward center. 20.Use of a device of claim 16, 17, 18 or 19 in a lens, prism, optical orphotographic filter.
 21. Use of a device of claim 16, 17, 18 or 19 in amicroscope, gunsight, telescope, binocular, endoscope, periscope,theodilite or microwave attenuation device.
 22. An electrochromic devicecomprising a lens having two plano-convex substrates having facesdisposed in opposing relation to each other and being coated with atransparent conducting material, an electrochromic layer coating theinside face of at least one of the substrates, an electrolyte layercontaining an electrolyte disposed between the substrates and means forsealing the lens.
 23. An electrochromic lens device comprising twoconcave substrates having faces disposed in opposing relation to eachother and being coated with a layer of transparent conductor material,an electrochromic layer coating at least one of the layers oftransparent conductor material, an electrolyte layer containing anelectrolyte and being disposed between the electrochromic layer and thelayer of transparent conductor material, and means for sealing the lens.24. An electrochromic prism device comprising a first substrate having aplanar face coated with a transparent conducting coating layer, a secondsubstrate having a planar face coated with stripes of transparentconductive coating, the coated planar faces being disposed in opposingrelation to each other, an electrochromic layer coating the transparentconductive coating of the second substrate, an electrolyte layercontaining an electrolyte and being disposed between the transparentconducting coating layer of the first substrate and the electrochromiclayer of the second substrate, and means for sealing the prism.
 25. Areflective modulator device comprising a first substrate having a planarface coated with a reflective coating layer and an electrochromic layercoating the reflective coating layer, a second substrate having a planarface disposed in opposing relation to the electrochromic layer of thefirst substrate and being coated with a conductive coating layer, theconductive coating layer having at least one aperture, an electrolytelayer containing an electrolyte and being disposed between theelectrochromic layer coating the first substrate and the conductivecoating layer coating the second substrate, and means for sealing thedevice.
 26. A reflective modulator device according to claim 25 whereinthe at least one aperture is a single hole, a single slit or amultiplicity of holes.
 27. A reflective modulator device according toclaim 25 or 26 wherein the aperture has a diameter less than thethickness of the electrolyte layer.
 28. A waveguide device comprising aplanar silicon substrate having a channel in a face of the substrate,the channel being coated with an electrochromic layer, a planarsubstrate having a conductive layer coating one face thereof, the facebeing disposed in opposing relation to the channel face of the siliconsubstrate, an electrolyte layer containing an electrolyte disposedbetween the conductive coating layer and the channel face of the siliconsubstrate, and means for sealing the device.
 29. A waveguide deviceaccording to claim 28 wherein the electrochromic layer comprisestungsten oxide and the layer fills the channel.
 30. A waveguide deviceaccording to claim 28 or 29 wherein the electrolyte layer has arefractive index lower than the refractive index of the electrochromiclayer.
 31. A microwave attenuator device comprising a planar substrate,a conductive film coating one face of the substrate, the film having aseries of offsetting parallel grooves in the surface of the film,electric terminals attached to the conductive firm, means forcontrolling the temperature of the device connected to the terminals,and a thermochromic film coating the conductive film.
 32. A microwaveattenuator device according to claim 31 wherein the conductive film ischrome, copper, gold or stainless steel and the thermochromic film isvanadium oxide.
 33. An electrochromic device for microwave attenuationcomprising two planar substrates having inside faces and outside faces,the faces being disposed in opposing relation to each other, a firstconductive coating layer coating at least one of the inside faces, anelectrochromic layer coating one of the first conductive coating layers,wherein the electrochromic layer comprises tungsten oxide, anelectrolyte layer containing an electrolyte disposed between theelectrochromic layer and the first conductive coating layer and a secondconductive coating layer coating at least one of the outside faces ofthe substrate and having an aperture therethrough.
 34. An electrochromicdevice for microwave attenuation comprising two planar substrates havinginside faces disposed in opposing relation to each other, two conductivecoating layers coating the inside face of each substrate, eachconductive coating layer comprising a series of longitudinal stripesarranged in parallel relation on the face of the substrate, anelectrochromic layer coating one of the conductive coating layers and anelectrolyte layer containing electrolyte disposed between theelectrochromic layer and conductive coating layer.
 35. An electrochromicdevice comprising two planar substrates having inside faces disposed inopposing relation to each other, an electrode layer comprising twoparallel stripes disposed along the edges of one of the inside faces andhaving a plurality of interdigitated fingers, an electrochromic layercoating the electrode layer, an insulating layer between the electrodelayer and the electrochromic layer and an electrolyte layer containingelectrolyte disposed between the electrochromic layer and the insideface of the opposed substrate.